286 research outputs found
Biology and new records of the invasive species Branchiomma bairdi (Annelida: Sabellidae) in the Mediterranean Sea
The first observations on the reproductive biology of the alien polychaete Branchiomma bairdi (McIntosh, 1885) (Sabellidae)
in the Mediterranean Sea are provided as well as additional Mediterranean records of the species, which can help to understand its
introduction and spreading. Re-examination of the specimens from Miseno harbour (Tyrrhenian Sea, Italy) revealed the presence
of B. bairdi in the central-Mediterranean since September 2004. The histological study of individuals collected in Malta revealed
that the species is a simultaneous hermaphrodite, developing male and female gametes in the same body segments; embryos are
brooded inside the parent tube. However, there is also evidence of asexual reproduction. The species shows a different reproductive
pattern from the previously reported population from the eastern-Pacific; this demonstrates its great plasticity and adaptability.
Branchiomma bairdi has an invasive behaviour, colonizing large areas in relatively short-time, and reaching relatively high densities
(c.a. 50 individuals/m2). Its expansion to several Mediterranean localities is largely a consequence of the high capacity of this
species to colonize extremely different habitats and substrates, the occurrence of sexual and asexual reproductive strategies, and
the combination of both. Furthermore, B. bairdi appears to be particularly abundant in confined areas and areas degraded due to
anthropogenic impacts. Finally, our findings strongly suggest that the pathway of introduction in the Mediterranean, previously
hypothesized as the Suez Canal (Lessepsian migration), is most likely via the Strait of Gibraltar
Diversidad de holoturoideos (Echinodermata:Holothuroidea) de la costa y plataforma continental de Asturias
Desde la década de los 70 se ha venido recolectando y conservando en la Colección del Departamento de Biología de Organismos y Sistemas (BOS) -Zoología-, macrofauna procedente de muestreos periódicos realizados en la zona intermareal de distintas localidades de la costa de Asturias (ría del Eo, Tapia de Casariego, Luanco, Gijón y Villaviciosa). Las tres localidades muestreadas más regularmente fueron Aramar (Luanco) -sustrato rocoso-, El Rinconín (Gijón) –sustrato rocoso- y El Puntal y La Ermita (Ría de Villaviciosa) -sustrato blando- Entre la fauna recolectada se encontraron numerosos ejemplares del grupo de los holoturoideos, pertenecientes a los órdenes Apodida, Aspidochirotida y Dendrochirotida.
En este trabajo se presentan datos sobre la diversidad de holoturoideos depositados en la colección del Departamento BOS procedentes de las localidades anteriormente mencionadas, así como del material procedente de las costas de la península Ibérica y de los archipiélagos Atlánticos de las islas Canarias y Cabo Verde. La identificación de especies se ha basado en la morfología externa, pero, sobre todo, en la extracción de escleritos dérmicos y el estudio de su forma, tamaño y distribución, lo cual tiene una mayor importancia como carácter taxonómico para la correcta determinación de las especies que la apariencia externa.
Finalmente, se presenta un listado actualizado de los holoturoideos registrados para las costas de Asturias, basado en datos propios y bibliográficos procedentes de las campañas oceanográficas “Cantábrico 83” y “CAP-89” realizadas en la plataforma costera cantábrica (López-Ibor A. 1987; De la Hoz J.J. & García L. 1991)
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Reconstruction and measurement of (100) MeV energy electromagnetic activity from π0 arrow γγ decays in the MicroBooNE LArTPC
We present results on the reconstruction of electromagnetic (EM) activity from photons produced in charged current νμ interactions with final state π0s. We employ a fully-automated reconstruction chain capable of identifying EM showers of (100) MeV energy, relying on a combination of traditional reconstruction techniques together with novel machine-learning approaches. These studies demonstrate good energy resolution, and good agreement between data and simulation, relying on the reconstructed invariant π0 mass and other photon distributions for validation. The reconstruction techniques developed are applied to a selection of νμ + Ar → μ + π0 + X candidate events to demonstrate the potential for calorimetric separation of photons from electrons and reconstruction of π0 kinematics
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Calibration of the charge and energy loss per unit length of the MicroBooNE liquid argon time projection chamber using muons and protons
We describe a method used to calibrate the position- and time-dependent response of the MicroBooNE liquid argon time projection chamber anode wires to ionization particle energy loss. The method makes use of crossing cosmic-ray muons to partially correct anode wire signals for multiple effects as a function of time and position, including cross-connected TPC wires, space charge effects, electron attachment to impurities, diffusion, and recombination. The overall energy scale is then determined using fully-contained beam-induced muons originating and stopping in the active region of the detector. Using this method, we obtain an absolute energy scale uncertainty of 2% in data. We use stopping protons to further refine the relation between the measured charge and the energy loss for highly-ionizing particles. This data-driven detector calibration improves both the measurement of total deposited energy and particle identification based on energy loss per unit length as a function of residual range. As an example, the proton selection efficiency is increased by 2% after detector calibration
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The Pandora multi-algorithm approach to automated pattern recognition of cosmic-ray muon and neutrino events in the MicroBooNE detector.
The development and operation of liquid-argon time-projection chambers for neutrino physics has created a need for new approaches to pattern recognition in order to fully exploit the imaging capabilities offered by this technology. Whereas the human brain can excel at identifying features in the recorded events, it is a significant challenge to develop an automated, algorithmic solution. The Pandora Software Development Kit provides functionality to aid the design and implementation of pattern-recognition algorithms. It promotes the use of a multi-algorithm approach to pattern recognition, in which individual algorithms each address a specific task in a particular topology. Many tens of algorithms then carefully build up a picture of the event and, together, provide a robust automated pattern-recognition solution. This paper describes details of the chain of over one hundred Pandora algorithms and tools used to reconstruct cosmic-ray muon and neutrino events in the MicroBooNE detector. Metrics that assess the current pattern-recognition performance are presented for simulated MicroBooNE events, using a selection of final-state event topologies
Convolutional Neural Networks Applied to Neutrino Events in a Liquid Argon Time Projection Chamber
We present several studies of convolutional neural networks applied to data
coming from the MicroBooNE detector, a liquid argon time projection chamber
(LArTPC). The algorithms studied include the classification of single particle
images, the localization of single particle and neutrino interactions in an
image, and the detection of a simulated neutrino event overlaid with cosmic ray
backgrounds taken from real detector data. These studies demonstrate the
potential of convolutional neural networks for particle identification or event
detection on simulated neutrino interactions. We also address technical issues
that arise when applying this technique to data from a large LArTPC at or near
ground level
The present and future status of heavy neutral leptons
The existence of nonzero neutrino masses points to the likely existence of multiple Standard Model neutral fermions. When such states are heavy enough that they cannot be produced in oscillations, they are referred to as heavy neutral leptons (HNLs). In this white paper, we discuss the present experimental status of HNLs including colliders, beta decay, accelerators, as well as astrophysical and cosmological impacts. We discuss the importance of continuing to search for HNLs, and its potential impact on our understanding of key fundamental questions, and additionally we outline the future prospects for next-generation future experiments or upcoming accelerator run scenarios
Tracking Signals of Change in Mediterranean Fish Diversity Based on Local Ecological Knowledge
One of the expected effects of global change is increased variability in the abundance and distribution of living organisms, but information at the appropriate temporal and geographical scales is often lacking to observe these patterns. Here we use local knowledge as an alternative information source to study some emerging changes in Mediterranean fish diversity. A pilot study of thirty-two fishermen was conducted in 2009 from four Mediterranean locations along a south-north gradient. Semi-quantitative survey information on changes in species abundance was recorded by year and suggests that 59 fish species belonging to 35 families have experienced changes in their abundance. We distinguished species that increased from species that decreased or fluctuated. Multivariate analysis revealed significant differences between these three groups of species, as well as significant variation between the study locations. A trend for thermophilic taxa to increase was recorded at all the study locations. The Carangidae and the Sphyraenidae families typically were found to increase over time, while Scombridae and Clupeidae were generally identified as decreasing and Fistularidae and Scaridae appeared to fluctuate in abundance. Our initial findings strongly suggest the northward expansion of termophilic species whose occurrence in the northern Mediterranean has only been noted previously by occasional records in the scientific literature
Network structure of vertebrate scavenger assemblages at the global scale: drivers and ecosystem functioning implications
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